Previously, an orthodontic appliance would include an arch wire which was anchored to teeth on opposite sides of the tooth or teeth to be straightened or repositioned. Usually, metal bands were placed over each tooth to be straightened, and a wire-receiving member or bracket spot-welded to each metal band. In other instances, the wire-receiving member or bracket was adhesively secured directly to the labial or buccal surface of the tooth. The arch wire would be given a bend or twist which would be inserted into the provided receiving channel of each bracket, the bend or twist being relied upon to apply pressure on the tooth in the right direction and in the right amount. Usually, several teeth require movement or straightening; and different angulation or twist of the bends may be required for each tooth. Such technique was not only difficult to make with any assurance that the pressure applied or resulting force vectors would be in the right direction and of the right amount to achieve the sought repositioning of the teeth, but repetition of a predicted force vector was also a problem, particularly where more than one orthodontist was working on the patient's teeth.
Stifter, U.S. Pat. No. 2,908,974, disclosed a bracket intended to improve upon the above-described prior art technique. In said patent, the disclosed bracket comprised an anchor member which is soldered to the metal band and a removable socket or channel member which interfits with the anchor portion. The socket member comprises one of an inventory of interchangeable socket members having wire-receiving sockets or channels which are differently arranged to apply differently directed pressures when the wire is caught therein so that allegedly no predetermined bends are necessary, the shape or inclination of the socket being relied upon to produce the desired vector. Stifter necessarily requires maintenance of a large inventory.
In Andrews, U.S. Pat. Nos. 3,447,128 and 3,660,900, one-piece metal cast brackets are disclosed having a plurality of dimensions built therein which allegedly, when coupled to an unbent arch wire, resulted in predictable force vectors being applied to the tooth. Some eight dimensions were taken into consideration. These included the curvature on the lingual side of the bracket, the radius of the curvature of the arch wire at the point of contact with the individual bracket, plus an angle or inclination which is built into the bracket socket or channel to effect torquing and tipping forces as well as in-out forces and tip compensation and rotation compensation angles as are often required in extraction cases. Such brackets being necessarily cast of one-piece metal, therefore, also require a considerable inventory on the part of the orthodontist in order to meet all force vector requirements with which he must deal in treating his patient. There is also the problem of different tooth sizes and shapes. Mistakes can be corrected only by replacement of the bracket.